Manufacture of grease



May 24, 1949. H, A, WOODS E1'- AL 2,470,965

\ MANUFACTURE oF GREASE` v Filed Jan. 18, 1947 Patented May 24, T949 UNITED STATES PATENT OFFICE MANUFACTURE F GREASE Company, San Francisc of Delaware o, Calif., a corporation Application ll'anuary 18, 1947, Serial No. 722,846

16 Claims.

This invention relates to a method of preparing greases. More particularly, this invention pertains to a novel process of making alkali and alkaline earth metal soap greases and to a new and novel method of statically cooling them in an enclosed system so as to obtain a product having a stable, smooth, buttery, homogeneous texture and consistency. In one of its specific embodiments, this invention pertains to a novel method of statically cooling alkali and alkaline earth metal soap greases in which soap is dissolved in mineral and/ or synthetic oil type bases in a plurality of elongated tubular Zones of desired diameter and length so as to cool statically said greases at a suiflciently rapid and uniform rate, thereby obtaining products having improved stability, consistency and texture. Instead of cooling greases in a plurality of elongated tubular zones or tubes, greases can be cooled in enclosed vessels of restricted cross-section oi not more than about 4 inches into which grease can be injected. This restricted space of the vessei can be of any convenient shape such as annular or rectangular, but should be of sufficient size so as to accommodate the volume of the hot greases entering therein. The cross-section into which the hot grease is injected is of restricted diameter or width in order to maintain efficient heat transfer so as to cool the grease rapidly and uniformly.

Various factors can and do influence final structure, consistency and texture of greases during manufacture; of these, the cooling is often most influential. The physical properties of greases made under identical conditions can be altered to a marked degree, depending on whether the cooling is ellected under agitation or under static conditions, or even when using different means of statically cooling these greases. The method and means employed in cooling greases, particularly greases of the class referred to above, to obtain an improved product, is not a simple matter, but is a fine art requiring great skill.

Lubricating greases of the type under consideration comprise mainly mixtures of oil and soap employed in suitable proportions, said mixtures on being heated to elevated temperatures so as to dissolve the soap in the oil form a homogeneous solution which when properly cooled forms greases. Factors which control and govern the structure, consistency and texture of grease products, include: the type and amount of soap used, the kind of oil employed, presence or absence of llers and other additives, and, of major importance, the method and conditions under which the greases are cooled. Proper and uniform cooling of greases from a molten state 2 otherwise a coarse, unstable, grainy or brous grease is obtained.

Present methods for cooling greases, are: (1) dynamic methods which include kettle and votator cooling and (2) static methods such as pan cooling and the like. Both of these methods for is of major importance and is essential for procooling greases under consideration are not particularly applicable since in practice it has been found that the resultant products are inferior in regard to both structure and stability.

One method of cooling a grease statically is to allow it to cool in a kettle having a cooling jacket around it through which air, water, or any other cooling medium can circulate and cool the kettle. In most cases this type of cooling eiiected in the same kettle used to compound the grease. However, the hot fluid grease can be transferred to a specially equipped kettle for cooling and a new batch of oil and soap can be added to the first kettle so as to have substantially an uninterrupted process for making grease. Still another method of cooling grease is to pour the hot grease directly into shipping or storage containers where they are allowed to cool. An improved method of cooling grease is to pour it into shallow pans or trays while in a hot fluid state and allow it to remain and cool to desired temperature. v

All of these methods of cooling have disadvantages when applied to lubricating greases which are cooled from a molten state. Greases of this type on cooling form what is known as false bodies and tend to crumble Aand disintegrate under pressure rather than retain a homogeneous structure. Since this gel-like formation in such greases cannot be avoided generally, it is at times necessary to homogenize such greases in order to break down the stiff gel structure. This results in a grease of softer but smoother and more uniform consistency.

In the cases of greases having a pronounced gel structure, it is essential and important that the gel structure bev uniformand stable with regard to oilseparation. To accomplish this, greases of this type must be cooled rapidly, at a controlled rate under static conditions. The kettle, tray container or any other known method of cooling these greases and particularly lithium soap greases usually result in undesirable products due to the factthatthey are poor in quality andappearance. This is due to the non-uniform heat transfer during cooling of the grease, which results in a stili, highly gelled surface while the center and other parts of the grease are soft, semi-liquid or even liquid.

Of the three above mentioned methods, the pan or tray cooling at present is the most desirable method of cooling greases because the trays are not of great depth. However, even with shallow pans it isdiincult to prevent a crust from forming at the surface which acts as a 3 heat insulator, inhibiting further rapidand uniform cooling of the grease. In addition, cooling greases by this method is a re hazard, particularly when the grease is poured into the pans at elevated temperatures and the oil employed in' making the grease has a low flash point.

It is an object of this invention to provide a method of quickly, simply, safely and economi cally making and cooling alkali and alkaline earth metal soap greases under static conditions. Another object of this invention is to provide a method of rapidly cooling alkali and alkaline earth metal soap greases in enclosed systems which result in a product' "of uniform consistency. Furthermore it is an object of this invention to statically cool greases in elongated tubular enclosed systems thus alleviating iire hazard. It is also an` object of this invention to' provide ra method of making and thereafter rapidly cooling under static conditions greases, particularly lithium soap Agreases, in narrow elongated tubes having uniformly controlled heat transfer so as to obtain greases of uniform consistency, desired texture, and good stability.

Broadlythis invention comprises a method of making alkali and alkaline earth metal soap greases and thereafter rapidly cooling them by disposing them preferably in enclosed relatively narrow elongated tubes having controlled heat transfer. The length ofthe tubes can be varied and is not a limitation; but the diameter should not exceed 4 inches and can vary from around about 1/4 to not more than about 4 inches. In most cases it is preferable to use tubes havinga die ameter of around about 21/2 to 31/2 inches because of the ease of filling and removing greases from such size tubes and because tubes of this size provide a sufficient heat transfer rate. The tubes or elongated grease coolers can be made of iron, steel, aluminum or alloys thereof or any material which provides suflicient heat transfer and which has no adverse catalytic effect upon the grease. The tubes can be cooled by circulating around the tubes air, water, brine or other cooling medium.

The time required for .cooling greases of the type and method under considerationgenerally depends upon the material from which the tubes are made, as well 4as-the cooling medium eme ployed. Usually it takes from a fraction of an hour to about 10 vhours for a grease to cool by the method of this invention. The preferred cooling time in 1A, to 3%/2 inch steel tube is between about 1A; to 3 hours for lithium soap grease. In addition to being more convenient and safer, cooling greases by this method eliminates the danger of contamination and oxidation.

The alkali and alkaline earth soaps used in making greases may be made by conventional methods, e. g. by* saponii'lcation of fats, fatty acids and the like with alkali and alkaline earth oxides or hydroxides of sodium, lithium, potassium, rubidium and cesium, beryllium, magnesium, calcium, strontium and barium, using one or several of the metals. Specieally the fatty materials used can be tallow, lard,- horse fat, fatty acids derived from vegetable oils such as castor oil, cotton-seed oil, rape oil, soya bean oil. corn oil and may be in hydrogenated or non-hydrogenated form. Fish oil and hydrogenated fish 'oil fatty acids, tall oil fatty acids, naphthenic acids, rosin oils synthetic fatty-acids., and synthetic acids produced by oxidizing paraiiin waxes also can be used as well as free fatty acids such as lauric, myristic, palmitic, stearic, arachic, behenic, oleic, ricinoleic, hydroxy stearic and the like.

It has been observed that the" type of base oil used has a marked influence upon the physical properties of greases. When compounding lithum soap grease it is preferable to use naphthenic type oils although other type oils can be used, since grease thus `compounded is less susceptible to bleeding and has improved temperature consistency characteristics. With other alkali and/or alkaline earth soaps, mineral oils of light, medium and heavy lubricating oil stocks derived from paranic, naphthenic or mixed crudes can be used as well asr synthetic lubricating stocks such as produced by polymerizing oleflnic materials in presence of Friedel-Craft catalyst, polymerizing alkylene oxides in presence of iodine, hydriodic acid and the like, Voltolizating mixtures of fixed and mineral oils, and those producedv from alkyl esters or organic acids,ve. g. 2-ethy1 hexyl sebacate, ethyl ricinoleate, dioctyl phthalate and the like.

The temperature to which oil and soap is heated to form a homogenous grease usually ranges from around about 350 to 500 F. A preferred temperature range when making lithium soap grease is around about 400 to 425 F.

The heating and mixing can be done in a heat* ing Votator or any other suitable piece of equipment. From there the hot liquid grease according to this invention goes directly to elongated cooling tubes Without lany intermediate treatment. The grease is cooled there under static conditions to a desired gelation state and thereafter forced out of the cooling tubes into a homogenizer where it is worked into a homogeneous mass and thereafter filled or packaged in suitable containers.

In order to more clearly set forth the invention reference is now made to the accompanying drawing, which is a iiow diagram illustrating a method of producing and subsequently cooling alkali soap greases by means of this invention. It is understood that modification as to equipment, its arrangement, type 4andkind of materials and their proportions can be resorted to without departing from the spirit of the invention as presented in the subjoined claims.

Referring to the flow diagram, it shows a slurry tank i into which is introduced calculated proportions of alkali or alkaline `earth metal soap and mineral oil through conduit 2. If other additives such as oxidation and corrosion inhibitors, anti-bleeding agents, oiliness agents, llers and the like are added to the grease they can be introduced into the slurry tank I through conduit 3 at a convenient time. The oil and soap is heated to between about 135 to 175 F.

and preferably i150 F. and then led through conduit 4 to conduit I4 and intofa heat exchanger 5. From the heat exchanger the mixture goes to a slurry homogenizer 6Y Where it is worked at a temperature of around about i200" F. The mixture can thengbe returned to the slurry tank I through lines IG and l5, for further working or by-passed through line I6 through pump 8 and into a heating Votator 7, anenclosed heat transfer mechanism manufactured by the Girdler Corporation, Votator Division, Louisville, Kentucky, and described in their bulir letin entitled The Votator. I f the mixture is returned to slurry 'tank l for further working it is subsequently discharged from the tank into line 4, through a booster pump 9 on through line 25 and pump 8 and into the heating Votator 1. The grease temperature in the heat Votator" 'l is kept at around about 400 to 500 F. and preferably around about 400 to 430" F. The utilization of a heat Votator for making grease is of considerable advantage over the open kettle method, since the Votator is entirely closed eliminating the danger of oil flashing and causing fire, The hot liquid grease from the "Votator is led along conduit I1 directly into a plurality of elongated cooling tubes I each tube having attached thereto control valve II. If desired other convenient enclosed shaped cooling vessels or containers 2| and 24 as shown in Figs. 2 and 4 can be substituted for the cooling tubes III shown in flow diagram 1. In Fig. 2, a transverse cross section taken on the line 3--3 thereof being shown in Fig. 3, the hot grease from "Votator 1 is inserted into the area marked 23 and is cooled by suitable means by space marked 22 and 2|. Fig. 4 may be a rectangular shaped body of restricted thickness but of relatively great length and height so that a large volume of grease can be injected into it and thereby eliminate the necessity of a large number of tubes as noted by iii in Fig. 1. If cooling tubes are used the grease is kept in them under static conditions until the gre-ase has cooled down sufhciently, to form a pronounced gel structure. The grease is then discharged through conduit I8 into a production or storage tank I2. There the grease is accumulated and then conducted through I9 into a homogenizer I3 where it is worked into a homogeneous mass at a temperature ranging from room temperature to around about i-150 F. The grease is then discharged through conduit 2d to suitable packing containers 26 ready for distribution. The grease in its production stages is conducted to or by-passed around certain equipment by means of conduits as noted in Fig. 1 each having attached thereto control valves I5'.

To illustrate the applicability of this cooling method for making grease, a specific example, namely, the method of making and cooling a lithium soap grease will be herein fully describedl following the flow diagram.

Around about 710% by weight of lithium stearate and a suitable amount of mineral lubricating oil, preferably naphthenic base oil are introduced into slurry tank I and agitated at a temperature of around about i150 F. The oilsoap mixture is then led through conduit 4 and Eli through heat exchanger and into slurry homogenizer where the mixture is homogenized at a temperature of around about 200 F. The composition is then conducted through lines I6 and i5 back to slurry tank I for further agitation and finally discharged at a temperature of about 150 F. through line 4 to pumps 9 and 8 and into heating Votator 7. There the oil-soap mixture is heated to about @125 F. and then discharged directly into a plurality of steel tubes Ill each having a diameter of about 3 inches and a length of about 40 feet. The grease is cooled statically in these tubes down to about 150 F. and forced out of them into a production or storage tank I 2. When suicient grease is accumulated in tank I2 it is conducted into a homogenizer I3 for working into a homogeneous consistency and texture, after which it is packed in containers 26. Grease produced by this method frequently requires less soap and has a consistency, texture and stability which is superior to any known grease produced and cooled by present known methods.

The composition of grease produced and cooled by this method can be modied and varied over. wide limits.4 Thus instead of making a straightl lithium stearate grease as disclosed above, mixture of lithium stearate and alkaline earth naphthenates or other soaps can be used. Also mixture of diierent metals as well as their acid radicals can be used in compounding grease. Thus a grease comprising sodium stearate, calcium naphthenate and lithium stearate can be made and then statically cooled by the method described.

To stabilize greases of the type described against oxidation it it advisable to add minor amounts of oxidation inhibitors to the grease. Among the antioxidants which are effective with grease composition of the type disclosed are: N-alkyl para phenylene diamine and condensed polynuclear aromatic mono-amines. Such inhibitors are N-butyl paraphenylene diamine, N-N-dibutyl para-phenylene diamine, etc. Also effective as oxidation inhibitors are alpha or beta naphthylamine, phenyl-alpha or beta naphthylamine, alpha-alpha, beta-beta, or alpha-beta dinaphthylamine, diphenylamine, tetra-methyl diamino diphenyl methane, petroleum alkyl phenols, and 2,4-di-tertiary butyl 6-methyl phenol.

Corrosion inhibitors which are particularly applicable with compositions of this invention are N-primary amines containing at least 6 and more than 18 carbon atoms in the molecule such as hexylamine, octylamine, decylamine, dodecyl-v amine, octadecylamine, heterocyclic nitrogen containing organic compounds such as alkyl substituted oxazolines and their salts illustrative examples being Alketerge-C and Alketerge-O, manufactured by Commercial Solvents Corp.,

' which compounds are fully described in U. S.

Patents 2,372,409 and 2,372,410.

Extreme pressure agents can be added to such grease and the preferred comprise esters of phosphorus acids such as triaryl, alkylhydroxy aryl, or aralkyl phosphates, thiophosphates or phosphites, etc., neutral aromatic sulfur compounds such as diaryl suldes and polysuli-ides, e. g. diphenyl sulde, dicresol sulide, dibenzyl sulfide, methyl butyl diphenol sulfide, etc., diphenyl selenide and diselenide: dicresol selenide and polyselenide, etc.: sulfurized fatty oils or esters of fatty acids and monohydric alcohols, e. g. sperm oil, jojoba oil, etc., in which the sulfur is tightly bound: sulfurized long-chain oleiins obtained by dehydrogenation or cracking of wax: sulfuriZed-phosphorized fatty oils, acids, esters and ketones, phosphorous acid esters having sulfurized organic radicals, such as esters of phosphoric or phosphorus acids with hydroxy fatty acids: chlorinated hydrocarbons such as chlorinated paraiiins, aromatic hydrocarbons, terpenes. mineral lubricating oil, etc.: or chlorinated ester of fatty acids containing the chlorine in position other than alpha position.

Additional ingredients which can be added are anti-bleeding agents such as lithium, calcium and strontium naphthenates, cresol, petroleum cresol and glycerine: anti-wear agents such as oilsoluble urea or thio-urea derivates, e. g., urethanes, allophanates, carbazides, carbazones, etc.; or rubber, polyisobutylene, polyvinylesters, etc.; VI improvers such as polyisobutylenes having a molecular weight above about 800, volatilized parain wax, unsaturated polymerized esters of fatty acids and monohydric alcohols, etc.: oiliness agents such as stearic and oleic acids and pour point depressors such as chlorinated naphthalene to further lower the pour point of the lubricant.

The amount 'of the above additives can be added to grease composition of this invention inV aromi-id about 01.01% to less than 110% by Weight, and preferably 0.1 to 5.0% by weight.

Greases prepared and lcooled by the methoddescribed have unusually smoothv textures, unifornlr consistency and are extremely stable over wide temperature ranges and for long periods. They are particularly `applicable for lubricating ball bearings used in aircrafts and various' mechanisms which required lubrication at teinper'atures ranging lfrom below -80 to about 350 F. for long periods.

We claim as our invention:

1. The method of cooling a grease comprising a major portion of mineral lubricating olli and between about 'I to 10% by weight lithium sten rate, between about 0.1. to 5.0% by weight calcium methane, from a temperature of i425 1F. by weight of an oxidation inhibitor selected from 'the'class consisting of N,N dibutylz para phenylene diamine, and tetramethyl diamine diphenyl methane, from a temperature of +425ya lF'. by forcing it from an enclosed heating and mixing. heatl transfer mechanism directly into a plurality of air cooledl narrow elongated steel. tubes having a diameter of between about 3 to 31/2 inches and said grease being kept in said tubes and cooled statically therein to a temperature of. around about 150 Fl, and passing it to a homogenizer for' working to a desired tcxziuxrel and uniform consistency.

2. The method of cooling a grease. comprising a major portion of mineral lubricating oil and be tween about 7 to 10% by 'weight lithium stearato, between about 0.1 to 5.0% by weight calcium naphthenate and between about 0.1 to 5.01% by weight of a corrosion inhibitor selected from. the class lconsisting of hexylamine, octylamine, dec'- ylaminei, dodecylamine, octadecylamin'e "and alkyl substituted oxazolines, from a temperature of 1:425" F. by forcing it from an enclosed heating and. mixing heat transfer mechanism directly into a plurality of air cooled narrow elongated. steel tubes having a diameter off. between about 3` to 3.1/2 inches and said. grease being kept said'tub'es and cooled statically therein to a terne perature of around about 150 F., 'and passing it to a homogenizer for working to a desired. tex@ ture and miiform consistency.

3. The method of cooling a vgrease comprising a major portion of mineral lubricating eiland between about 7 to 10% by weight lithitu-n'` hydroxy stearato, between about 0.1 to"5.0% by weight calcium naphthenate and between about 0.1 to 5.0% by weight of a corrosionv inhibitor selected from the class consisting of hexylamine, octylamine, decylamine, dodecylamine,v octade'c ylarinlne and alkyl substituted oxazolines, from `a temperature of i425 F, by forcing it from an enclosed heating and mixing heat transfer mechanism directly into a plurality oral-rA narrow elongated steel tubes rhaving a 'diameter of between about 3' to 3% inches and said; grease being kept in said. tubes and cooled staticai'ly therein to a temperature of around 150" Ff., and'. passing it to ahomogenizer for Working to 'a desired texture and uniform consistency.

4. The -method of cooling a grease comprising a major portion of mineral lubricating and between about 7 to 10% by Weight lithium palmitate, between about 0,1 to '5.0% by' weight calcium naphthenate and betweenabout 0.1v to 5.0% .by weight of a corrosioninhibitor selected from the class consisting of hexylamine, octyla- PLO' 8 and' ai'ykl. substituted oxazolines, from a temperature'of .Li-425 F; by forcing it from an enclosed'heatmgand mixing; heat transfer mechanisnr directly into a plurality of air cooled narrow elongated steel tubes having a diameter of between. about 3 to inches and said grease being kept in said tubes and cooled statically thereiirtoa temperature of around. about 150 and passing it toy ahomogenizer for working. to

-a desired texture and uniform. consistency.

5. In: a process of preparing lithium soap grease comprising a major proportion of mineral lubricatlngfoiif and a minor amount of lithium stearato, sufficient to impart a pronounced gel structure to said: grease when uniorrnlyV cooled, the method of 'rapidly and uniformly cooling said grease which comprises, forcing the' grease from an enclosed heating and mixing heat transfer mechamsm while inv a liquid state at a temperature of from about 100 up to about. 425 F.. and higher directly into a plurality of air cooled narrow elongated steel tubes having. a diameter of about 3 up to about 31/2r inches, said. grease being kept in said tubes and cooled statically therein substantially at a uniform andl uninterruptedv rate for a period sufficient for the grease to form a pronounced gel structure throughout and have adesiredl texture and. uniform consistency.

d. In a processv of preparing lithium soap grease comprising. a major'proportion of a mixture of mineral lubricating oil and 2ethyl hexyl sebacate and. a minor amount of lithium stearato, suiilcifent to impart a pronounced gel structure to. grease when uniformly cooled', the method of. rapidly and uniformly cooling said grease which-comprises, forcing th-e grease from. an enclosed heating and mixing heat transfer mechanism while in a liquid state at a temperature of from about 100 up to about 425' F. and higher directly `into a plurality of air cooled narrow elongated steel tubes having a diameter of about 3 up to about 31/2 inches, said grease beingv kept in. said tubes and cooled statically therein substantially at a uniform and uniterrupted rate for a period sufiicient for the' greasetoform a pronounced gel structure throughout and have a desirecl and uniform consistency.

7. In aprocess of preparing. lithium soap grease comprising a mador pro-portion of. mineral lubrieating oil and minor amounts` of lithium soap of high molecular weightmonocarboxylicacids and their mixtures., sufiicientto impart a pronounced gelV structure to said grease when cooled, the method of rapidly and uniformly cooling said v grease-,which comprises forcing the grease from an enclosed heating and mixing heat transfer mechanism While in a hot liquid state directly into ia plurality of. air cooled narrow elongated steel tubes ranging in diameter from between about 21/2 to-notmore. than 31/2 inches, said grease being kept in said tubes and cooled statically therein substantially at a uniform and uninterrupted rate for a period suihcent for the grease to form a pronounced gel structure throughout and have.

a desired texture and uniform consistency.

8l Ina processof preparing. barium soap grease, the method of rapidly and uniformly cooling said grease by forcing it from an enclosed heating andmix-ing heat transfer mechanism while ina hot liquid stater directly into ar plurality of air cooled narrow elongated steel tubes having a diameter of from between about 21/2 to not more than 31/2'. inches sai-d grease being kept in said tubes 'and cooled statically therein substantially mine, decyla'ml'ne, dodecylamine, octadecylamine 7o at a uniform and uninterrupted rate for a period 9 sufficient for the grease to form a desired texture and uniform consistency.

9. In a process of preparing sodium soap grease comprising a major proportion of mineral lubrieating oil and a minor amount of sodium soap of high molecular weight monocarboxylic acid, the method of rapidly and uniformly cooling said grease by forcing it from an enclosed heating and mixing heat transfer mechanism while in a hot liquid state, directly into a plurality of air cooled narrow elongated steel tubes having a diameter of from between about 21/2 to not more than 31/2 inches and said grease being kept in said tubes and cooled statically therein substantially at a uniform and uninterrupted rate for a period sumcient for the grease to form a desired texture and uniform consistency.

10. In a process of preparing alkali and alkaline earth soap grease of high molecular weight monocarboxylic acid and their mixtures comprising a d major proportion of mineral lubricating oil and substantially minor amounts of said soap, sunlcient to impart a pronounced gel structure to said. grease on cooling, the method of rapidly and uniformly cooling said grease, which comprises forcing the grease from an enclosed heating and mixing heat transfer mechanism while in a hot liquid state directly into a plurality of air cooled narrow elongated steel tubes ranging in diameter from between about 21/2 to not more than 31/2 inches, said grease being kept in said tubes and cooled statically therein substantially at a uniform and uninterrupted rate for a period sufficient foi` the grease to form a pronounced gel structure throughout and have a desired texture and uniform consistency.

1l. In a process of preparing alkali and alkaline earth soap grease of high molecular weight monocarboxylic acid and their mixtures comprising a major proportion of a suitable organic lubricating base and substantially minor amounts of said soap, sufficient to impart a pronounced gel struc-4 ture to said grease on cooling, the method of rapidly and uniformly cooling said grease, which comprises forcing the grease from an enclosed heating and mixing heat transfer mechanism while in a hot liquid state directly into a plurality of air cooled narrow elongated steel tubes ranging in diameter from between about 21/ to not more than 31/2 inches, said grease being kept in said tubes and cooled statically therein substantially at a uniform and uninterrupted rate for a period sumcient for the grease to form a pronounced gel structure throughout and have a de-A sired texture and uniform consistency.

12. In a process of preparing alkali and alkaline earth soap grease comprising a major proportion of a mixture of mineral oil and Z-ethyl hexyl sebacate as the base and substantially minorl amounts of said soap, sufficient to impart a pro-A nounced gel structure to said grease on cooling, the method of rapidly and uniformly cooling said grease, which comprises forcing said hot liquid state grease from an enclosed heating and mixing zone directly into a plurality of narrow elongated tubular zones ranging in diameter from between about 1/4 to not more than about 4 inches, each tubular zone allowing for good heat transfer and cooled by suitable means, said grease being kept in said tubular zones and cooled statically therein substantially at a uniform and uninterrupted rate for a period suflicient for the grease to form a pronounced gel structure throughout and have a desired and uniform consistency.

13. In a process of preparing alkali and alkaline earth soap grease, the method of rapidly and uniformly cooling such grease, which comprises forcing the grease at a temperature from between about 400 up to about 500 F. from an enclosed heating and mixing heat transfer mechanism directly into a plurality of cooled narrow elongated steel tubes ranging in diameter from between about 21/2 to not more than about 31/2 inches, said grease being kept in said tubes and cooled statically therein substantially at a uniform and uninterrupted rate for a period suicient for the grease to form a pronounced gel structure throughout and have a desired texture and uniform consistency.

14. In a process of preparing alkali and alkaline earth metal soap grease, the method of rapidly and uniformly cooling such grease which comprises forcing the hot liquid state grease from an enclosed heating and mixing zone directly into a plurality of narrow elongated tubular zones ranging in diameter from between about 21/2 inches to not more than about 31/2 inches, each tube allowing for good heat transfer and cooled by materials from the class consisting of air, water, and brine, said grease being kept in said tubular zones and cooled statically therein substantially at a uniform and uninterrupted rate for a period suflicient for the grease to form a pronounced gel structure throughout and have a desired texture and uniform consistency.

15. In a process of preparing alkali and alkaline earth metal soap grease, the method of rapidly and uniformly cooling the hot grease which comprises forcing the hot liquid state grease from an enclosed heating and mixing zone directly into a plurality of narrow elongated tubular zones ranging in diameter from between about 1/4 to not more than about 4 inches, each tubular zone allowing for good heat transfer and cooled by suitable means, said grease being kept in said tubular zones and cooled statically therein substantially at a uniform and uninterrupted rate for a period suflcient for the grease to form a pronounced gel structure throughout and have a desired tex-` ture and uniform consistency.

16. In a process of preparing alkali and alkaline earth metal soap greases, wherein the hot grease is rapidly and uniformly cooled, the improvement which comprises forcing the hot liquid state grease from an enclosed heating and mixing zone directly into a zone of restricted cross-section having a thickness of not more than about 4 inches and cooled by suitable means, said grease being kept in said cooling zone and cooled statically therein substantially at a uniform and uninterrupted rate for a period sucient for the grease to form a pronounced gel structure throughout and have a desired texture and uniform consistency.

HAROLD A. WOODS. WALLACE J. YATES. LEENDERT KLINGEN. ROBERT C. BARTON.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,332,202 calkins oct. 19, 1943 2,343,736 Beerbower et al. Mar. 7, 1944 2,394,567 Sproule et al. Feb. 12, 1946 2,417,495 I-Ioulton Mar. 18, 1947 

